This application claims priority to Japanese Patent Application No. P2000-267765 filed on Sep. 4, 2000 in Japan, and Japanese Patent Application No. P2000-314315 filed on Oct. 13, 2000 in Japan. The contents of the aforementioned applications are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a fuel cell where an electrode film structure comprising a solid polymer electrolyte film with an anode electrode and a cathode electrode on the opposite sides thereof is clamped with a pair of separators. More specifically, the present invention relates to a fuel cell where assembly and sealability between the electrodes and the separators is improved.
2. Description of the Related Art
For example, there has been developed a solid polymer electrolyte type fuel cell constituted by laminating a plurality of units, with one unit being such that an electrode film structure provided with an anode electrode and a cathode electrode at opposite positions with a solid polymer electrolyte film inserted therebetween is clamped by separators, and this has been utilized for various practical applications.
One example of this fuel cell will be described with reference to FIG. 23. In this figure, reference symbol 1 denotes a solid polymer electrolyte film, and on opposite sides of this solid polymer electrolyte film 1, there are respectively arranged an anode electrode 2 and a cathode electrode 3, having a smaller area than that of the solid polymer electrolyte film 1. Sealing members 4 and 5 for gas seal are arranged on the respective outer peripheral portions of the anode electrode 2 and the cathode electrode 3.
The above sealing members 4 and 5 have seal lips 6 provided integrally and protrudingly on respective surfaces opposite to the surface contacting with the solid polymer electrolyte film 1, so as to surround the electrode surface of the anode electrode 2 and the cathode electrode 3.
A separator 8 exhibiting a fuel gas supply function and a power collecting function, and having guide grooves 7 for the fuel gas is arranged on the outside of the anode electrode 2 facing the anode electrode 2, so as to come in contact with the anode electrode 2. Likewise, a separator 10 exhibiting an oxidant gas supply function and a power collecting function and having guide grooves 9 for the oxidant gas is arranged on the outside of the cathode electrode 3 facing the cathode electrode 3, so as to come in contact with the cathode electrode 3.
The thus constructed fuel cells are laminated in a plurality of numbers, and the laminated body is fastened in the lamination direction by a fastening device (not shown) to thereby constitute a fuel cell as a stack.
In the above described fuel cell, differences in thickness between the anode electrode 2 and cathode electrode 3, and the sealing members 4 and 5 can be absorbed by the seal lip 6. As a result, the anode electrode 2 and the separator 8, and the cathode electrode 3 and the separator 10 can be brought into good contact with each other, and hence this feature is excellent in contributing to the improvement of the cell performance (see Japanese Patent No. 2922132).
In the above described prior art however, there is a problem in that it is difficult to set the sealing members 4 and 5 and the anode electrode 2 and the cathode electrode 3 without causing misalignment, at the stage of superimposing the sealing members 4 and 5 on the solid polymer electrolyte film 1. If misalignment occurs between the sealing member 4 on the anode electrode 2 side and the sealing member 5 on the cathode electrode 3 side in the direction along the surface of the solid polymer electrolyte film 1, the positions where the seal lips 6 come close to the separators 8 and 10 shift slightly. As a result, the reaction force for the seal by the seal lips 6 acting on the solid polymer electrolyte film 1 on the base side of the seal lips 6 is biased, and hence an unbalanced force acts on the solid polymer electrolyte film 1, thereby causing problems such as the solid polymer electrolyte film 1 slips or folds occur therein. As a result, a problem occurs in that the dimensional accuracy at the time of assembling the anode electrode 2 and the sealing member 4, and the cathode electrode 3 and the sealing member 5 must be strictly controlled, thereby making production difficult.
Also in the solid polymer electrolyte type fuel cell, even if the solid polymer electrolyte film 1, the anode electrode 2 and the cathode electrode 3 are overlapped, since these are as thin as several hundreds microns in the thickness direction, a sufficient height dimension for the seal lips 6, that is, sufficient elastic deformation cannot be ensured, thereby causing a problem in the sealability.
Moreover, if the margin for compression of the seal lip 6 is increased so as to ensure the sealability, the fastening force in a condition with the fuel cells laminated increases, thereby causing an increase in size of the fastening member, an increase in size of the fastening apparatus, and a problem in that the separators 8 and 10 cannot endure the fastening force and may be damaged.
On the other hand, there is a case where a seal structure is adopted in which a groove is formed in the separator, the sealing members are set stably in the groove without causing misalignment, and the sealing member is closely contacted with the corresponding portion. FIG. 24 and FIG. 25 show this example, wherein a seal S having a seal body having a square shape in cross-section is inserted into a groove 11 in the separators 8 and 10. The seal S has a fin F at a corner thereof, and the insertion stability of the seal S is ensured by this fin F. Therefore, at the time of inserting the seal S into the groove 11, the seal S can be inserted with torsion of the seal S being kept to a minimum. FIG. 24 shows a case where the fin F is provided on the both sides, and FIG. 25 shows a case where the fin F is provided on one side.
In such a structure however, in either case of the seal S shown in FIG. 24 and FIG. 25, when the seal S is inclined, the seal height decreases from H1 to H2, and the load applied to the seal S causes displacement in the direction of compression, as shown by the arrows in the figure, and a moment load acts thereon. As a result, the reaction force for the seal differs depending on the place, causing a problem in that uniform sealability cannot be obtained.
It is therefore an object of the present invention to provide a fuel cell for which assembly of the seals is facilitated and with excellent sealability, and which enables miniaturization.
In order to solve the above problems, the invention according to a first aspect is characterized by a fuel cell (for example, a fuel cell N in this embodiment) where an electrode film structure (for example, an electrode film structure 12 in this embodiment) having an anode electrode (for example, an anode electrode A in this embodiment) provided on one side of a solid polymer electrolyte film (for example, a solid polymer electrolyte film 15 in this embodiment), and a cathode electrode (for example, a cathode electrode C in this embodiment) provided on the other side thereof is clamped with a pair of separators (for example, a separator 13 on the anode side and a separator 14 on the cathode side in this embodiment), wherein a groove (for example, a groove 38 in this embodiment) is provided on a separator surface corresponding to the outer peripheral portion of the anode electrode or the cathode electrode (for example, surfaces 13a, 14a in this embodiment), and a seal (for example, a seal S1 in this embodiment) having a circular shape in cross-section and with a fin (for example, a fin F in this embodiment) is provided in this groove.
By having such a construction, it becomes possible to set a high seal height for the seal in the groove and increase the sectional area of the assembled seal. As a result, when the fuel cells are laminated and fastened, the surface pressure change of the seal portion becomes gradual with respect to the compressive load. Therefore there is the effect that differences in the seal stress between the respective fuel cells can be reduced, assembly of the seals is facilitated and excellent sealability can be ensured. As a result, there is the effect that the bending stress on the separators decreases, and damage of the separators can be reliably prevented.
Furthermore by making the seal have a circular shape in cross-section, a low compressive load can be realized and the ratio of the surface area to the volume of the seal can be reduced. Therefore there is the effect that durability with respect to heat, such as compressive permanent deformation can be improved.
Moreover, since it is possible to prevent inclining of the seal by means of the fin, there is the effect that linearity of the seal can be maintained, distortion, slippage and waving at the time of assembly can be eliminated, and alignment of the mounting position is facilitated. Moreover, also in the case where inclining of the seal occurs, since the compression margin of the seal having a circular shape in cross-section does not change, there is the effect that causes of poor sealing can be eliminated.
Furthermore, since it is possible to identify inclining of the seal by means of the visually identifiable direction of the fin, there is the effect that assembly of the seal can be performed quickly, enabling a reduction of manufacturing time. Moreover, when inserting the seal into the groove, insertion can be done by fitting the fin into the groove. Therefore there is the effect that the seal can be inserted appropriately without causing distortion or waving of the seal.
Furthermore, since the fin is formed, and the tensile strength of the seal can be increased by this fin, there is the effect that in the case where adherence to the mold occurs at the time of mold removal after vulcanization molding, even if excessive pulling or stretching is applied at the time of peeling off, occurrence of cuts, cracks and ruptures can be reduced, thereby improving yield.
The invention according to a second aspect is characterized by a fuel cell where an electrode film structure having an anode electrode provided on one side of a solid polymer electrolyte film and a cathode electrode provided on the other side thereof is clamped with a pair of separators, wherein there are provided in the separator, communicating holes for supplying and discharging a reactant gas containing a fuel gas (for example, an inlet side fuel gas communicating hole 22a and an outlet side fuel gas communicating hole 22b in this embodiment), communicating holes for supplying and discharging a reactant gas containing an oxidant gas (for example, an inlet side oxidant gas communicating hole 23a and an outlet side oxidant gas communicating hole 23b in this embodiment) and communicating holes for supplying and discharging a coolant (for example, an inlet side coolant communicating hole 24a and an outlet side coolant communicating hole 24b in this embodiment), penetrating through the separator, and a groove (for example, a groove 39 in this embodiment) is provided around the periphery of at least one of the opposing communicating holes, and a seal (for example, a seal S2 in this embodiment) having a circular shape in cross-section and with a fin is provided in this groove.
By having such a construction, it becomes possible to increase the seal height of the seal in the grooves and increase the sectional area of the assembled seal, as in the first aspect, at the periphery of the communicating holes for supplying and discharging a reactant gas containing a fuel gas, the communicating holes for supplying and discharging a reactant gas containing an oxidant gas and the communicating holes for supplying and discharging a coolant provided in the separator. As a result, when the fuel cells are laminated and fastened, the surface pressure change of the seal portion with respect the compressive load becomes gradual. Therefore there is the effect that differences in the seal stress between each fuel cell can be reduced, and hence the bending stress on the separators decreases, and damage of the separators can be reliably prevented.
Moreover by making the seal a circular shape in cross-section, a low compressive load is realized and the ratio of the surface area to the volume of the seal can be reduced. Therefore there is the effect that durability with respect to heat, such as compressive permanent deformation can be improved.
Furthermore, since it is possible to prevent inclining of the seal by means of the fin, there is the effect that the linearity of the seal can be maintained, distortion, slippage and waving at the time of assembly can be eliminated, and alignment of the mounting position is facilitated. Moreover, also in the case where inclining of the seal occurs, since the compression margin of the seal having a circular shape in cross-section does not change, there is the effect that causes of poor sealing can be eliminated.
Furthermore, since it is possible to identify inclining of the seal by means of the visually identifiable direction of the fin, there is the effect that assembly of the seal can be performed quickly, enabling a reduction of manufacturing time. Moreover, when inserting the seal into the groove, insertion can be done by fitting the fin into the groove. Therefore there is the effect that the seal can be inserted appropriately without causing distortion or waving of the seal.
Furthermore, since the fin is formed, and the tensile strength of the seal can be increased by this fin, there is the effect that in the case where adherence to the mold occurs at the time of mold removal after vulcanization molding, even if excessive pulling or stretching is applied at the time of peeling off, occurrence of cuts, cracks and ruptures can be reduced, thereby improving yield.
The invention according to a third aspect is characterized by a fuel cell obtained as one unit by laminating a plurality of sets of electrode film structures having an anode electrode provided on one side of a solid polymer electrolyte film and a cathode electrode provided on the other side thereof, which are clamped with a pair of separators, wherein a coolant channel (for example, branching channel grooves 35 in this embodiment) is formed between the separators with backsides (for example, surfaces 13b and 14b in this embodiment) abutting each other, and a groove (for example, a groove 39 in this embodiment) is provided in at least one of the separator surfaces (for example, the surface 13b in this embodiment), at a portion surrounding the channel, and a seal having a circular shape in cross-section (for example, a seal S1 in this embodiment) and with a fin is provided in this groove.
By having such a construction, at the periphery of the coolant channel formed between adjacent separators, as in the above described first and second aspects, it becomes possible to increase the seal height of the seal in the groove and increase the sectional area of the assembled seal. Hence, when the fuel cells are laminated and fastened, the surface pressure change of the seal portion becomes gradual with respect to the compressive load. Therefore there is the effect that differences in the seal stress between the respective fuel cells can be reduced, and hence the bending stress on the separators decreases, and damage of the separators can be reliably prevented.
Furthermore by making the seal have a circular shape in cross-section, a low compressive load can be realized and the ratio of the surface area to the volume of the seal can be reduced. Therefore there is the effect that durability with respect to heat, such as compressive permanent deformation can be improved.
Moreover, since it is possible to prevent inclining of the seal by means of the fin, there is the effect that linearity of the seal can be maintained, distortion, slippage and waving at the time of assembly can be eliminated, and alignment of the mounting position is facilitated. Moreover, also in the case where inclining of the seal occurs, since the compression margin of the seal having a circular shape in cross-section does not change, there is the effect that causes of poor sealing can be eliminated.
Furthermore, since it is possible to identify inclining of the seal by means of the visually identifiable direction of the fin, there is the effect that assembly of the seal can be performed quickly, enabling a reduction of manufacturing time. Moreover, when inserting the seal into the groove, insertion can be done by fitting the fin into the groove. Therefore there is the effect that the seal can be inserted appropriately without causing distortion or waving of the seal.
Furthermore, since the fin is formed, and the tensile strength of the seal can be increased by this, there is the effect that in the case where adherence to the mold occurs at the time of mold removal after vulcanization molding, even if excessive pulling or stretching is applied at the time of peeling off, occurrence of cuts, cracks and ruptures can be reduced, thereby improving yield.
The invention according to a fourth aspect is characterized by a fuel cell obtained as one unit by laminating a plurality of sets of electrode film structures having an anode electrode provided on one side of a solid polymer electrolyte film and a cathode electrode provided on the other side thereof, which are clamped with a pair of separators, wherein there are provided in the separator, communicating holes for supplying and discharging a reactant gas containing a fuel gas, communicating holes for supplying and discharging a reactant gas containing an oxidant gas and communicating holes for supplying and discharging a coolant, penetrating through the separator, and a groove is provided around the periphery of at least one of the opposing communicating holes of the separators of the fuel cell with backsides abutting each other, and a seal having a circular shape in cross-section and with a fin is provided in this groove.
By having such a construction, at the periphery of each communicating hole formed between adjacent separators, as in the above described first through third aspects, it becomes possible to increase the seal height of the seal in the groove and increase the sectional area of the assembled seal. Hence, when the fuel cells are laminated and fastened, the surface pressure change of the seal portion becomes gradual with respect to the compressive load. Therefore there is the effect that differences in the seal stress between the respective fuel cells can be reduced, and hence the bending stress on the separators decreases, and damage of the separators can be reliably prevented.
Furthermore by making the seal have a circular shape in cross-section, a low compressive load can be realized and the ratio of the surface area to the volume of the seal can be reduced. Therefore there is the effect that durability with respect to heat, such as compressive permanent deformation can be improved.
Moreover, since it is possible to prevent inclining of the seal by means of the fin, there is the effect that linearity of the seal can be maintained, distortion, slippage and waving at the time of assembly can be eliminated, and alignment of the mounting position is facilitated. Moreover, also in the case where inclining of the seal occurs, since the compression margin of the seal having a circular shape in cross-section does not change, there is the effect that causes of poor sealing can be eliminated.
Furthermore, since it is possible to identify inclining of the seal by means of the visually identifiable direction of the fin, there is the effect that assembly of the seal can be performed quickly, enabling a reduction of manufacturing time. Moreover, when inserting the seal into the groove, insertion can be done by fitting the fin into the groove. Therefore there is the effect that the seal can be inserted appropriately without causing distortion or waving of the seal.
Furthermore, since the fin is formed, and the tensile strength of the seal can be increased by this, there is the effect that in the case where adherence to the mold occurs at the time of mold removal after vulcanization molding, even if excessive pulling or stretching is applied at the time of peeling off, occurrence of cuts, cracks and ruptures can be reduced, thereby improving yield.
The invention according to a fifth aspect is characterized in that a width dimension xe2x80x9caxe2x80x9d of the groove is set to a range of from 2.0 to 4.0 mm, and a depth dimension xe2x80x9cbxe2x80x9d is set to a range of from 0.05 to 1.0 mm.
By having such a construction, it becomes possible to ensure an appropriate compressibility based on the lower limit of the seal diameter that can be manufactured stably, while ensuring the strength of the separator. Therefore there is the effect that the sealability can be ensured without damaging the separator. Moreover, it also becomes possible to clear the restriction on the outer peripheral dimension of the separators and to cope with differences in the minimum seal size. Hence, there is the effect that miniaturization of the fuel cell becomes possible, and the seals can be reliably fitted.
The invention according to a sixth aspect is characterized in that the seal is formed of a seal body having a circular shape in cross-section and a fin extending from the seal body in the width direction of the seal, and a diameter dimension xcfx86 of the seal body is set to a range of from 0.5 to 1.6 mm, and a width dimension L of the entire seal is set to a range of from 1.0 to 3.1 mm.
By having such a construction, it becomes possible to set the fin in a range that can be identified visually, and the entire seal can be made with a width dimension that allows misalignment at the time of setting the seal. Hence, there is the effect that the seals can be attached reliably, while visually identifying distortion of the seals.